全文获取类型
收费全文 | 42381篇 |
免费 | 7708篇 |
国内免费 | 9982篇 |
专业分类
测绘学 | 2015篇 |
大气科学 | 9136篇 |
地球物理 | 11144篇 |
地质学 | 20982篇 |
海洋学 | 4710篇 |
天文学 | 2094篇 |
综合类 | 4884篇 |
自然地理 | 5106篇 |
出版年
2024年 | 123篇 |
2023年 | 584篇 |
2022年 | 1683篇 |
2021年 | 1929篇 |
2020年 | 1635篇 |
2019年 | 1856篇 |
2018年 | 2281篇 |
2017年 | 2067篇 |
2016年 | 2445篇 |
2015年 | 1914篇 |
2014年 | 2422篇 |
2013年 | 2399篇 |
2012年 | 2207篇 |
2011年 | 2308篇 |
2010年 | 2362篇 |
2009年 | 2334篇 |
2008年 | 2116篇 |
2007年 | 2036篇 |
2006年 | 1644篇 |
2005年 | 1578篇 |
2004年 | 1234篇 |
2003年 | 1273篇 |
2002年 | 1205篇 |
2001年 | 1170篇 |
2000年 | 1495篇 |
1999年 | 2238篇 |
1998年 | 1797篇 |
1997年 | 1866篇 |
1996年 | 1713篇 |
1995年 | 1465篇 |
1994年 | 1323篇 |
1993年 | 1125篇 |
1992年 | 871篇 |
1991年 | 680篇 |
1990年 | 528篇 |
1989年 | 448篇 |
1988年 | 429篇 |
1987年 | 281篇 |
1986年 | 228篇 |
1985年 | 166篇 |
1984年 | 107篇 |
1983年 | 93篇 |
1982年 | 96篇 |
1981年 | 74篇 |
1980年 | 61篇 |
1979年 | 53篇 |
1978年 | 22篇 |
1976年 | 17篇 |
1975年 | 16篇 |
1958年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
141.
For a Hamiltonian that can be separated into N+1(N\geq 2) integrable parts, four algorithms can be built for a symplectic integrator. This research compares these algorithms for the
first and second order integrators. We found that they have similar local truncation errors represented by error Hamiltonian
but rather different numerical stability. When the computation of the main part of the Hamiltonian, H
0, is not expensive, we recommend to use S
* type algorithm, which cuts the calculation of the H
0 system into several small time steps as Malhotra(1991) did. As to the order of the N+1 parts in one step calculation, we found that from the large to small would get a slower error accumulation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
142.
143.
144.
张众服 《大地测量与地球动力学》1996,(4)
利用三峡地区多年的地形变观测资料,分析了该区的地形变特征。结果表明,各断层活动性甚微或基本不活动,区域地壳相对稳定 相似文献
145.
黑色高岭石粘土岩,是铜川王石凹煤矿石炭纪煤系地层顶部,五号煤层的上部一层稳定的煤矸石。经偏光显微镜及费氏台测试光性特征、化学试验及分析鉴定表明,这是一种由高岭石组成的,成分很纯、颗粒大、结晶良好的高岭石粘土岩。据微量元素含量分析,此高岭石系淡水沉积物。 相似文献
146.
E. Biémont P. Palmeri P. Quinet G. Paquin Z. G. Zhang G. Somesfalean S. Svanberg 《Monthly notices of the Royal Astronomical Society》2001,328(4):1085-1090
Lifetimes of six levels belonging to the 4f10 6p configuration of Ho iii have been measured for the first time using the time-resolved laser-induced fluorescence method. They are compared with multiconfigurational pseudo-relativistic Hartree–Fock calculations. A very good agreement is found. Using the experimental lifetimes and theoretical branching fractions, a first set of transition probabilities of astrophysical interest has been obtained for this ion. 相似文献
147.
本文探讨了利用地震矩反演断裂形变带运动学参数的基本理论和方法,将其初步应用于鲜水河断裂形变带变形分析和运动机制的研究。结果表明,鲜水河断裂带呈现出走向拉伸、倾向压缩的形变格局,由地震矩反演的断裂带剪切形变速率(10.9mm/a)与用地质学估算方法(17mm/a)和现今地壳形变测量(8mm/a)的结果相当。同时,反演出的应变主方向能解释鲜水河断裂现今活动分段性特征以及多种滑动方式共存的现状,从而证明该方法是目前研究区域运动学问题切实有效的手段之一。 相似文献
148.
The characteristics of red karst weathering crust in the research region can be divided into three subtypes. The first one includes the silicon to aluminum ratio, the composition of the clay minerals, etc., and reflects the weak action of de-silicon and aluminum enrichment. The second one, for example the granularity, shows that the viscous action is strong. The third one, such as the CaCO3 content and pH value, has regional difference in a large scale, which is consistent with the condition of modern scenery, so it is not important as for the ancient environment.
相似文献149.
1 INTRODUCTION Active oxygen free radicals can damage cell structure, even kill the cells, causing aging and cer- tain serious diseases (Bors et al., 1989). Usually, the production and scavenging of active oxygen free radicals are in balance in healthy hu… 相似文献
150.
The subtle interactions between the magnetohydrodynamics (MHD) and transverse plasmons are investigated. It is shown that there is a resistive instability by the plasmon's soliton in a current sheet, which eventually turns into an eruptive instability at the magnetic field reconnection. In the case of ion-acoustic turbulence, the high temperature current sheet model must adopt the aromalous conductivity instead of the Coulomb conductivity. The numerical results are consistent with the observations obtained by Hanaoka (1994). Thus the flare caused by X-ray loop coalescence can be basically interpreted by this model of magnetic field reconnection driven by ponderomotive force. 相似文献